California High-Speed Rail Authority 

Fresno to Bakersfield 

Section 

Draft Supplemental 

Environmental Impact 

Report/Environmental 

Impact Statement 

Appendix 3.4-C 

Noise and Vibration Mitigation 

Guidelines 

November 2017
Appendix 3.4-C 

Noise and Vibration Mitigation Guidelines 

November 2017 California High-Speed Rail Authority 

Fresno to Bakersfield Section 

Draft Supplemental EIR/EIS 

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Table of Contents

California High-Speed Rail Authority November 2017

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TABLE OF CONTENTS 

ACRONYMS AND ABBREVIATIONS ....................................................................................3.4-C-iii 

APPENDIX 3.4-C: NOISE AND VIBRATION MITIGATION GUIDELINES ............................ 3.4-C-1

3.4-C-1 APPENDIX: NOISE AND VIBRATION MITIGATION GUIDELINES ........... 3.4-C-1
Table of Contents 

November 2017 California High-Speed Rail Authority 

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Acronyms and Abbreviations

California High-Speed Rail Authority November 2017

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ACRONYMS AND ABBREVIATIONS 

Authority California High-Speed Rail Authority 

dB decibel(s) 

dBA A-weighted decibel(s)

FRA Federal Railroad Administration 

HSR high-speed rail 
Acronyms and Abbreviations 

November 2017 California High-Speed Rail Authority 

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Appendix 3.4-C 

Noise and Vibration Mitigation Guidelines 

California High-Speed Rail Authority November 2017

Fresno to Bakersfield Section Page | 3.4-C-1 

Draft Supplemental EIR/EIS 

APPENDIX 3.4-C: NOISE AND VIBRATION MITIGATION GUIDELINES 

3.4-C-1 APPENDIX: NOISE AND VIBRATION MITIGATION GUIDELINES 

Introduction 

This appendix describes the noise mitigation that must be considered when noise impacts are 

identified. Please note that the following information was previously provided in Technical 

Appendix 3.4-A of the Fresno to Bakersfield Section Final Environmental Impact 

Report/Environmental Impact Statement but has been incorporated into a separate appendix for 

the sake of clarity. 

Noise Mitigation Guidelines 

In general, noise mitigation must be considered when impacts are identified. Mitigation guidelines 

for the three impact categories identified by Federal Railroad Administration (FRA) are as follows: 

 No Impact: No mitigation required.

 Moderate Impact: Mitigation may be considered at the discretion of the California High-Speed

Rail Authority (Authority), and implementation would be subject to reasonable project-specific

factors related to effectiveness, cost, density, and proximity of sensitive receivers.

 Severe Impact: Consideration of mitigation is required if impacts cannot be avoided. The

Authority will take steps to reduce noise substantially through mitigation measures that are

reasonable, physically feasible, practical, and cost-effective.

Mitigation of Severe Noise Impacts 

The Authority will examine alternatives to avoid, minimize, or mitigate severe noise impacts. If 

severe noise impacts cannot be avoided, then the Authority will take steps to reduce severe noise 

substantially through mitigation measures that are reasonable, physically feasible, practical, and 

cost-effective. The following criteria will be used for evaluating the reasonableness of noise 

barriers as mitigation for severe noise impacts: 

 Calculations and Computations for barrier geometry as stated in the FRA High Speed Noise

and Vibration assessment, Table 5-3.

 Increase over existing noise levels.

 Number of noise sensitive sites affected.

 The minimum number of affected sites should be at least 10, and the length of a noise barrier

should be at least 800 feet.

 Barrier heights up to a maximum of 14 feet will be considered. Mitigation options for areas

that require barriers over 14 feet will be studied on a case by case basis.

 The cost limit for a noise barrier would be set at $55,000 (2010 dollars) per benefited

residence.

 The community should approve of implementation of the recommended noise barriers

(75 percent of all affected parties).

Section 4(f) and Section 106 properties with severe or moderate noise impacts will require 

mitigation, will not be subject to these guidelines, and will be evaluated on a case-by-case basis. 

Substantial Noise Reduction 

A minimum outdoor noise reduction of 5 decibels (dB) using the applicable criterion for the 

property is considered substantial. 
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Reasonable 

Reasonableness implies that good judgment and common sense have been applied during the 

decision-making process. Reasonableness is determined on the basis of several factors 

regarding the individual circumstances and the specific needs of affected receivers. 

Physically Feasible 

Noise mitigation measure must be designed, constructed, installed, or implemented in 

compliance with structural requirements related to ground conditions, wind loading, seismic risk, 

safety considerations, accessibility, material maintainability and longevity, and applicable 

engineering design practices and technology. Noise mitigation measures must not result in an 

adverse environmental impact, such as significant visual intrusions, blocked views, or adverse 

effects to a historical site. 

Sound barriers are the most common noise mitigation measure. The maximum sound barrier 

height would be 14 feet for at-grade sections; however, all sound barriers should be designed to 

be as low as possible to achieve a substantial noise reduction. Berm and berm/wall combinations 

are the preferred types of sound barriers where space and other environmental constraints 

permit. 

On aerial structures, the maximum sound barrier height would also be 14 feet, but barrier material 

would be limited by engineering weight restrictions for barriers on the structure. Sound barriers on 

the aerial structure should still be designed to be as low as possible to achieve a substantial 

noise reduction. 

Visual Effects 

Noise mitigation measures must be designed, constructed, installed, and implemented in a 

manner that does not result in adverse impacts to the visual resources in the area. Sound barriers 

will consist of a solid barrier no more than 6 feet in height. Above 6 feet, the sound barrier will be 

made of transparent materials. For example, a 13-foot-high sound barrier would consist of 6 feet 

of solid material on the bottom topped by 7 feet of transparent material. 

Cost Effectiveness 

The cost for constructing a noise barrier along the at-grade portion of the alignment is estimated 

to be $57.60 per square foot, and the cost to construct a noise barrier along the elevated portion 

of the alignment is $48 per square foot. The total cost of mitigation cannot exceed $55,000 per 

benefitted receiver. This cost is determined by dividing the total cost of the mitigation measure by 

the number of noise-sensitive buildings that receive a substantial (i.e., 5 dBA [A-weighted 

decibels] or greater) outdoor noise reduction. This calculation will generally limit the use of 

mitigation in rural areas that have few and/or isolated residential buildings. If the density of 

residential dwellings is insufficient to make the measure cost-effective, then other noise 

abatement measures, such as sound insulation, will be considered on a case-by-case basis. If 

sound insulation is identified as an alternative mitigation measure, the treatment must provide a 

substantial increase in noise reduction (i.e., 5 dBA or greater) between the outside and inside 

noise levels for interior habitable rooms. 

Mitigation Parameters 

 Prior to operation of the high-speed rail (HSR), the Authority will install sound barriers where

they can achieve between 5 and 15 dB of noise reduction, depending on their height and

location relative to the tracks. The primary requirements for an effective sound barrier are that

the barrier must (1) be high enough and long enough to break the line-of-sight between the

sound source and the receiver, (2) be of an impervious material with a minimum surface

density of 4 pounds per square foot, and (3) not have any gaps or holes between the panels

or at the bottom. Because many materials meet these requirements, aesthetics, durability,

cost, and maintenance considerations usually determine the selection of materials for sound

barriers (examples are shown in Figure 3.4-14). Depending on the situation, sound barriers

can become visually intrusive. Typically, the sound barriers style is selected with input from
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the local jurisdiction to reduce the visual effect of barriers on adjacent lands uses. For 

example, sound barriers could be solid or transparent, and made of various colors, materials, 

and surface treatments. 

 The Authority will work with the communities to identify how the use and height of sound

barriers would be determined using jointly developed performance criteria. Other solutions

may result in higher numbers of residual impacts than reported herein. Options may be to

reduce the height of sound barriers and combine barriers with sound insulation or to accept

higher noise thresholds than the FRA’s current noise thresholds.

 If sound walls are not proposed or do not reduce sound levels to below a severe impact level,

building sound insulation can be installed. Sound insulation of residences and institutional

buildings to improve the outdoor-to-indoor noise reduction is a mitigation measure that can be

provided when the use of sound barriers is not feasible in providing a reasonable level (5 to

7 dB) of noise reduction. Although this approach has no effect on noise in exterior areas, it

may be the best choice for sites where sound barriers are not feasible or desirable and for

buildings where indoor sensitivity is of most concern. Substantial improvements in building

sound insulation (on the order of 5 to 10 dB) can often be achieved by adding an extra layer

of glazing to windows, by sealing holes in exterior surfaces that act as sound leaks, and by

providing forced ventilation and air conditioning so that windows do not need to be opened.

Performance criteria would be established to balance existing noise events and ambient

roadway noise conditions as factors for determining mitigation measures.

 If sound walls or sound installation is not effective, the Authority can acquire easements on

properties severely affected by noise. Another option for mitigating noise impacts is for the

authority to acquire easements on residences likely to be impacted by HSR operations in

which the homeowners would accept the future noise conditions. This approach is usually

taken only in isolated cases where other mitigation options are infeasible, impractical, or too

costly.

 The decision to include mitigation assessments may depend on factors such as the number

of noise-sensitive sites affected, the relative increase in noise levels, the sensitivity at

affected land uses, the effectiveness of mitigation measures, community views, costs versus

benefits, design limitations, whether sensitive use is solely indoors, and safety. For example,

where land-use activity is solely indoors, an interior day-night sound level, dBA, criterion of

45 dBA from project sources is recommended to determine whether building sound insulation

improvements should be considered for mitigation.

Federal Transit Administration/Federal Railroad Administration Construction

Noise Mitigation 

1. Design considerations and project layout:

 Construct noise barriers, such as temporary walls or piles of excavated material, between

noisy activities and noise-sensitive receivers.

 Route truck traffic away from residential streets, if possible. Select streets with the fewest

homes, if no alternatives are available.

 Site equipment on the construction lot as far away from noise-sensitive sites as possible.

 Construct walled enclosures around especially noisy activities or around clusters of noisy

equipment. For example, shields can be used around pavement breakers and loaded

vinyl curtains can be draped under elevated structures.

2. Sequence of operations:

 Combine noisy operations so they occur in the same time period. The total noise level

produced will not be significantly greater than the level produced if the operations were

performed separately.
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 Avoid nighttime activities. Sensitivity to noise increases during the nighttime hours in

residential neighborhoods.

3. Alternative construction methods:

 Avoid impact pile driving where possible in noise-sensitive areas. Drilled piles or the use

of a sonic or vibratory pile driver are quieter alternatives where the geological conditions

permit their use.

 Use specially quieted equipment, such as quieted and enclosed air compressors, and

mufflers on all engines.

 Select quieter demolition methods, where possible. For example, sawing bridge decks

into sections that can be loaded onto trucks results in lower cumulative noise levels than

impact demolition by pavement breakers.

 The environmental assessment should include a description of one or more mitigation

approach for each affected location.

Federal Transit Administration/Federal Railroad Administration Construction 

Vibration Mitigation 

1. Design considerations and project layout:

 Route heavily loaded trucks away from residential streets, if possible. Select streets with

fewest homes, if no alternatives are available.

 Operate earthmoving equipment on the construction lot as far away from vibrationsensitive sites as possible.

2. Sequence of operations:

 Phase demolition, earthmoving, and ground-impacting operations so as not to occur in

the same time period. Unlike noise, the total vibration level produced could be

significantly less when each vibration source operates separately.

 Avoid nighttime activities. People are more aware of vibration in their homes during the

nighttime hours.

3. Alternative construction methods:

 Avoid impact pile driving where possible in vibration-sensitive areas. Drilled piles or the

use of a sonic or vibratory pile driver causes lower vibration levels where the geological

conditions permit their use.

 Select demolition methods not involving impact, where possible. For example, sawing

bridge decks into sections that can be loaded onto trucks results in lower vibration levels

than impact demolition by pavement breakers, and milling generates lower vibration

levels than excavation using clam shell or chisel drops.

 Avoid vibratory rollers and packers near sensitive areas.

Construction Noise and Vibration Mitigation Guidelines 

All construction activities in this report were analyzed in terms of their noise impacts in regards to 

FRA recommended guidelines. Local jurisdictions provide construction noise exempt times where 

the FRA guidelines are followed. A majority of construction will be conducted during these 

construction noise exempt times, but when construction is conducted outside of the construction 

noise exempt times, construction noise must abide by local noise standards. Proper mitigation 

may be necessary in order to avoid noise impacts at nearby noise-sensitive receivers. 

Pile driving activities conducted during the grade separation and elevated track structure 

construction phases would be the loudest noise generating activity during construction of the high 

speed train corridor. As previously mentioned, residences within a distance of 410 feet of grade 
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separation construction activities that include pile driving, or within 430 feet of elevated track 

structure construction activities that include pile driving, would be exposed to noise levels greater 

than the 80 dBA equivalent sound level threshold. 

 Piles that are required for structure along the HSR corridor and which would be located within

500 feet of a noise sensitive receiver should be installed using the drilling and casing method.

If the drilling and casing method were used, maximum noise levels associated with construction 

activities would drop by 11 dB, and the distances to the 80 dBA equivalent sound level contour 

would decrease from 410 feet to 180 feet for grade separation construction activities, and 

decrease from 430 feet to 220 feet for elevated track structure construction activities. Another 

method to mitigate noise related to pile driving is the use of an augur to install the piles instead of 

a pile driver which would reduce noise levels substantially. If pile driving is necessary, limit the 

time of day the activity can occur. 

The most effective way to minimize the impact of construction noise during the development of 

the project is to enforce the time restrictions for the hours of construction as listed in local noise 

ordinances. It is important for the design engineer to plan the order of operations during 

construction so that the noise levels resulting from construction operations will not exceed local 

noise ordinances or those recommended by the FRA. To avoid unnecessary annoyance from 

construction noise, the following best practices for construction noise control should also be 

considered for inclusion in construction contract documents: 

 All noise-producing project equipment and vehicles using internal combustion engines shall

be equipped with mufflers and air-inlet silencers, where appropriate, in good operating

condition that meet or exceed original factory specifications. Mobile or fixed “package”

equipment (e.g., arc-welders, air compressors) shall be equipped with shrouds and noise

control features that are readily available for that type of equipment.

 All mobile or fixed noise-producing equipment used on the project, which is regulated for

noise output by a local, state, or federal agency, shall comply with such regulation while in

the course of project activity.

 Material stockpiles and mobile equipment staging, parking, and maintenance areas shall be

located as far as practicable from noise-sensitive receivers.

 Material stockpiles should be used to block line of sight to nearby noise-sensitive receivers

when possible.

 Locating fixed noise-generating equipment as far from noise-sensitive land uses as is

practical.

 Limit the loudest construction activities, such as concrete breaking and jack hammering, to

the middle of the day when the sensitivity to such noises will be minimal. Noise-producing

signals, including horns, whistles, alarms, and bells shall be used for safety warning purposes

only.

 No project-related public address or music system shall be audible at any adjacent receiver.

 If complaints arise, the contractor shall initiate a construction noise monitoring plan to ensure

the construction noise levels at the nearest noise-sensitive land uses are within the limits of

the noise ordinance.

 Avoid nighttime construction in residential neighborhoods.

 During nighttime work, use smart back-up alarms, which automatically adjust the alarm level

based on the background level, or switch off back-up alarms and replace with spotters.

 Re-route construction-related truck traffic along roadways that will cause the least

disturbance to residents.

 Implement noise-deadening measures for truck loading and operations.
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 Minimize the use of generators to power equipment.

 Grade surface irregularities on construction sites.

 Use of temporary noise barriers shall be considered where project activities and equipment

are unavoidably close to noise-sensitive receivers.

 Use of on-site trailers and containers as temporary barriers between any fixed construction

noise source and nearby sensitive receivers.

 All workers involved with the construction of this project must be protected from excessive

noise exposure as mandated by the Occupational Safety and Health Administration, which

has regulated worker noise exposure to a time-weighted-average of 90 dBA over an 8-hour

work shift. Areas where levels exceed 85 dBA must be designated and labeled as high-noiselevel areas where hearing protection is required.

Construction Vibration Mitigation 

After locating potential vibration impacts due to construction with the use of the procedure 

outlined above, mitigation may be necessary to ensure that there will be no vibration impacts at 

sensitive receivers. Changes in the design and project layout, changes in the sequence of 

operations, and using alternative construction methods are all available vibration mitigation 

options. 

When the engineers design the project and the layout of the project, heavily loaded trucks can be 

re-routed away from residential streets and onto streets with fewer homes. Earthmoving 

equipment on the construction lot should also be operated as far as possible from sensitive 

receivers. Changes in the sequence of operations can also mitigate vibration impacts at sensitive 

receivers. Construction activities that cause high levels of vibration should be staggered so that 

multiple sources of vibration are not occurring at once. Nighttime construction activities should 

also be avoided. Alternative construction methods are also an acceptable vibration mitigation 

option. If pile driving does occur, impact pile driving should be avoided near vibration-sensitive 

areas. A sonic or vibratory pile driver will generate lower vibration levels at sensitive receivers. 

Demolition methods not involving impacts should be used when possible. The utilization of 

vibratory rollers and packers should be avoided near vibration-sensitive receivers.